[Ugadog]

Courtesy of RoverGGM (in the FJ Cruiser Forum):

Seat belt chime
1. Turn the ignition switch on (without starting car)
2. Press the ODO/TRIP switch until the odometer displays "ODO"
3. Turn the ignition switch off
4. Turn the ignition switch on
5. Press ODO/TRIP switch immediately (within 6 seconds after turning the power switch ON) and hold it down for 10 seconds or more.
6. Continue holding the ODO/TRIP switch and fasten the front passenger's seat belt.
7. Check that the odometer displays either "b-on" or "b-off" (it will be "b-on")
8. Press the ODO/TRIP button to change the display to "b-off".
9. Turn the ignition switch off.
10. Turn the ignition switch on while depressing the brake pedal.
11. Check that no buzzer sounds when setting on the front passenger seat.